Microhabitat factors determine the distribution of two invasive Helianthus species in hybrid zones of Argentina

CANTAMUTTO MIGUEL; MONDON ANA LAURA; POVERENE MÓNICA

Mar del Plata

Congreso; 2nd World Conference on Biological Invasions and Ecosystem Functioning; 2011

2nd World Conference on Biological Invasions and Ecosystem Functioning

Helianthus annuus (ANN) and H. petiolaris (PET) are two non-native plant invaders relative to domesticated sunflower. Usually these species grow under different ecological conditions; nevertheless there are several hybrid zones (HZ) in central Argentina where both species grow together. Hybridization and gene flow among them in those HZ could increase their invasiveness. In the HZ invaders show a tendency to grow very close but as separate pure stands. To investigate if biotic and abiotic microhabitat parameters determine the species distribution, six HZ of Buenos Aires and La Pampa provinces were surveyed. The populations grew along dirt roadsides, covering rather rectangular surfaces (≤1ha) extended across short distances (<1km). Plant population composition in the HZ comprises ca. 6.5 103 ANN, 3.2 103 PET and 0.4 103 plantsin mixed stands of both species (MIX) reaching high densities (≤40 plants/m2). Principal coordinates analysis failed to differentiate the microhabitat plant community considering the predominance of the 27 occurring plant species. Multivariate analysis showed that ANN grows alone in microhabitat sites of the HZ with deeper soils, higher organic matter content, moreavailable P, lower pH, and lower sand content. On the other hand PET inhabits soils with the opposite conditions. The MIX stands grow in intermediate soil conditions. This results show for the first time that abiotic microhabitat factors influence the spatial distribution of Helianthus species in the HZ.